Modern spectrometry offers rich possibilities by convenient use either of interferometric devices (Fourier transform spectrometry) or of selective modulation (grid spectrometry). Progresses in resolution and luminosity have been spectacular in the last decade, and new domains of high resolution and low luminosity have been explored. In those cases of extreme performances, the instruments are generally highly sophisticated, delicate, and expensive. Nevertheless, Fourier transform spectroscopy is now developing for pratical applications. We have examined the possibilities of interferometric devices to routine spectral analysis in chemistry, biology, pollution, detection etc ... and are now aware of the interesting characteristics of those mountings by the fact that they are luminous, flexible and very simple. They need no com-puter and are very suitable for low resolutions. We shall describe first the basic principle, and later focus on the various possibilities resulting from the direct access to the interferogram and the application of the mathematical properties of the Fourier transform : Fourier derivation, Fourier correlation with a reference spectrum, Fourier correlation of derivatives etc ... Moreover when the spectrum has a quasi periodic structure a very simple interferometric device can be used and has proved to be very efficient for the detection of some atmospheric pollutants (SO2, NO2).